The present invention relates to a lighting fixture. More particularly, it relates to a lighting fixture which can be adjusted to direct the maximum candlepower of the lamp and reflector system of the lighting fixture at a desired vertical angle, and which includes a rotatable glareshield which can be adjusted to prevent glare from the lamp and reflector system of the lighting fixture from being viewed by persons present in the space illuminated by the lighting fixture.
A ceiling washer is a lighting fixture which is designed to uniformly illuminate the ceiling of a particular space by projecting light across the ceiling. The light is typically generated by a lamp, the output of which is intensified and directed by a system of reflectors. Several different designs have been employed to prevent glare from the lamp and reflector system from causing discomfort to those occupying the space lit by the ceiling washer. One such design involves concealing the lamp and reflector system in a buildin element, such as a cove located below the edges of the ceiling. Another approach has been to conceal the lamp and reflector system in a box which is mounted on a wall and provided with an open top. Yet another approach has been to provide a visor which protrudes from the bottom of the frame of the lamp and reflector system to shield the glare of the lamp and reflector system from the eyes of those occupying the illuminated space.
The degree of shielding necessary to prevent glare from being seen by those occupying the space depends on the geometry of the space illuminated by the lighting fixture and the height at which the lighting fixture is positioned. For example, where a lighting fixture is mounted in a room with a low ceiling, and therefore must be mounted at a low height, the sightline of persons occupying the room is such that the shielding provided must block the glare from the lamp and reflector system at a greater vertical angle than would be required in a room with a high ceiling where the fixture can be mounted at a greater height.
Likewise, the degree of shielding necessary depends on the size of the room to be illuminated, since the height at which glare is visible above the shield decreases as the horizontal distance between the viewer and the lighting fixture increases, assuming that at least some portion of the lamp and reflector system capable of creating glare is higher than the top of the shield.
Greater shielding is of course achieved by increasing the height of the shield; however, the greater the height of the shield is, the less effective the lighting fixture is as a ceiling washer. This is because a ceiling washer illuminates the greatest area of ceiling most uniformly when the maximum candlepower of the lamp and reflector system is directed far out across the ceiling, i.e., when the angle at which maximum candlepower is directed, as measured from a vertical line drawn upward from the lighting fixture, is large. The optimum value of the angle varies depending on the area and shape of the ceiling to be illuminated and the vertical distance between the lighting fixture and the ceiling. When light is projected at such a large angle, a high shield may block some of the light which otherwise would shine on the ceiling. Therefore, the shield should be made only as high as is required to prevent visible glare. Nonetheless, in some cases, the height of the shield required in a particular space to shield a lamp and reflector system which is designed to project its maximum candlepower at the "optimum" angle for the same space may be such that the maximum candlepower of light projected by the lamp and reflector system is actually blocked by the shield. In such circumstances, greater efficiency would be achieved by projecting the maximum candlepower of the lamp and reflector system in a more vertical direction so that more of the projected light reaches the ceiling.
In view of the foregoing, it would be desirable to be able to provide a lighting fixture which has an adjustable lamp and reflector system and an adjustable shield, both of which may be adjusted for use in various lighting arrangements to efficiently shield the glare created by the lamp and reflector system of the lighting fixture and to effectively light the surface desired.
It would also be desirable to be able to provide a means for easily mounting and removing the adjustable shield such that the shield and associated housing for the lighting fixture can be installed after the lighting fixture has been wired in place, and such that the shield and housing may be changed at a later time.